The invention relates to a device for diverting discrete cleaning bodies from the main stream of a fluid flowing through a tubular heat exchanger, this device consisting of a diverter casing through which an axial current passes and a separating sieve system disposed therein having at least one sieve surface disposed at an angle to the flow and terminating at its downstream end in a lateral outlet connection, the sieve surface being pivoted for cleaning purposes such that the upstream side of the sieve surface can be changed to the downstream side.
Such an apparatus is already known from German AS No. 1,227,040. Such apparatus are used in self-cleaning tubular heat exchangers operating with cleaning bodies which are forced through the tubes by the medium (cooling water for example) flowing through the tubes, in order to thus scrape away the impurities settling on the walls and thus constantly to keep the heat exchanger clean. Sponge rubber balls or the like are usually used as the cleaning bodies, their diameter being slightly greater than the diameter of the heat exchanger tubes. To be able to remove the cleaning bodies from the heat exchanger fluid, the above-mentioned device is placed in the discharge from the heat exchanger and serves to separate the cleaning balls from the heat exchanger fluid. The cleaning bodies emerging from the lateral outlet connection can then, if desired, be aspirated together with a small portion of the heat exchanger fluid by means of a return pump, and they can be returned through a connecting line into the input line of the tubular heat exchanger.
The known device consists of a tubular casing having a diameter corresponding to the diameter of the heat exchanger outlet line. In this tubular casing there are two sieves, an upper sieve and a lower sieve. The upper sieve is formed by two sieve surfaces extending from the walls at an angle to the direction of flow and merging with one another in the center of the casing to form a kind of hopper through which the cleaning bodies are guided into the lower sieve, while the heat exchanger fluid passes substantially through the openings in the sieve and moves in a substantially unhindered laminar flow through the cylindrical casing. The lower sieve consists of a box which is disposed in the center of the tubular casing and is attached to the horizontal edge of the upper sieve and consists again of sieves disposed in a hopper-like manner with respect to one another. Both the two upper sieves and the lower sieves are each mounted rotatably in the casing and can be rotated from without for the purpose of cleaning the sieve by reverse flushing. Due to the numerous shafts which become necessary for the operation of the different sieves, a great number of openings in the tube are required which, since they have to be provided with packings, make the manufacturing costs great, on the one hand, but on the other hand they also make the apparatus require a great deal of maintenance. Especially in the case of reactor applications, where radioactive substances might be carried in the heat exchanger medium, it is extremely important that the circuit be absolutely leak-proof.
Another disadvantage is that the cleaning bodies gather substantially in the center of the cylindrical casing and from there they first have to be carried over to the casing wall before they can emerge from the casing. In the arrangement represented in FIG. 1 of German AS 1,227,040, of a lateral outlet connection leading radially outwardly, transport problems can arise on account of the sharp turn involved. If the lateral outlet connection is attached at an angle to the direction of flow so as to avoid the sharp bend, the structural length of the apparatus is increased. It would be desirable, therefore, to bring the cleaning bodies together, not in the center of the apparatus, but instead in the vicinity of the outer wall.
A system of this kind is shown in German Patent No. 2,612,905, in which only one sieve surface disposed at an angle to the direction of flow is provided, which terminates at its downstream end in a lateral outlet connection which actually is situated in the vicinity of the wall and therefore greatly facilitates the withdrawal of the cleaning bodies. In this patent, it is also found that the acute angle that develops in this embodiment between the sieve surface and the casing wall can cause the cleaning bodies to become wedged between them. Cleaning bodies which become caught in this manner then usually cause additional cleaning bodies to become entrapped, resulting in the formation of great clusters which then interfere with or even block the exit of the cleaning bodies, and additionally they unacceptably increase the resistance to the flow of the exchange fluid.
German Patent No. 2,612,905 seeks to prevent this wedging of cleaning bodies by making the lateral outlet tube a tube running along the margin of a portion of the elliptical boundary between the sieve surface and the casing wall. A similar construction is also shown in German AS No. 2,612,917 except that here the withdrawal of the cleaning bodies takes place in the center of the casing. In both cases any pile-up of the cleaning bodies is supposed to be largely prevented by the arrangement of the tubes, which are slotted and in which a turbulence is formed by the flow of the exchanger fluid. A disadvantage is in this case to be seen in the fact that the design is again relatively complex, and in particular many difficult welds are required for the purpose of avoiding the creation of dead spots in the pipe connection due to inaccurate workmanship, where cleaning bodies can again pile up, possibly resulting in a change of the conditions of flow and thus additional pile-ups of cleaning bodies, until finally the entire system for the aspiration of the cleaning bodies is stopped up. A design similar to that of German Patent No. 1,227,040 is also seen in German Patent No. 1,303,750; note should also be taken of German Patents Nos. 862,456 and 894,699, which were the first to deal with this process for the self-cleaning of heat exchangers.